What happened
On August 1, 2008, at 6:30 AM, an Atec Zephyr 2000 ultralight, identified as EC-ZIX, was departing from Montélimar aerodrome for a flight to Perpignan. The aircraft, operated privately, was part of a group of ultralight pilots participating in a cross-country tour of France. During the takeoff roll on runway 20, the pilot aligned the aircraft mid-runway on the unpaved surface. As the aircraft reached a speed of approximately 60 km/le, it encountered a rut in the runway. This impact caused the aircraft to lift off the ground without pilot input.
Surprised by the sudden lift, the pilot applied back-pressure on the control column. This inappropriate elevator input caused the aircraft to roll sharply to the left, leading the left wingtip to strike the ground. The aircraft then pivoted 90 degrees to the left and struck the ground with a heavy nose-down attitude, eventually coming to rest in a vertical position. The accident resulted in two injuries (the pilot and one passenger) and the total destruction of the aircraft.
The investigation
Investigators examined the wreckage and found that the flaps were set to the takeoff position and the elevator trim was set to neutral. No mechanical failures or malfunctions were identified prior to the accident. The investigation also focused on the aircraft's weight and balance. The total weight of the pilot and passenger was 180 kg, with 25 kg of luggage and 40 kg of fuel.
Findings
- The primary cause of the accident was the pilot's inappropriate reaction to the unexpected takeoff, specifically the application of elevator input that induced a roll.
- A significant contributing factor was the insufficient consideration of the aircraft's performance characteristics, as the aircraft was overloaded by 70 kg beyond its maximum authorized takeoff mass.
- The aircraft's stall speed in takeoff configuration at maximum weight is 64 km/h, meaning the aircraft was operating at a critical speed threshold when the runway rut triggered the lift-off.